1. Field of the Invention
The present invention relates to the field of agricultural engineering and is specifically concerned with automatic coupling devices to connect the hydraulic system of a tractor with that of a tractor-drawn means.
The invention may be used to connect the hydraulic system of a tractor with the hydraulic dump cylinder of a dump trailer or with the actuating hydraulic cylinder of a self-contained loader on a trailer.
The invention may be employed to the best advantage to connect the hydraulic systems of a tractor and of a drill, a cultivator, or another hydraulically-operated agricultural machine.
2. Description of the Prior Art
The problem of a reliable automatic coupling of the tractor and tractor-drawn means hydraulic systems without complicating the construction of the coupling device remains yet to be adequately solved.
There has been proposed, for example, an automatic coupling device which has unions, provided with seals, to be brought into an operative engagement (USSR Inventor's Certificate No. 178,251, Int. Cl..sup.2 F 16L 37/04, published Mar. 26, 1963).
This device has no shut-off members, in particular shut-off valves, in the unions and is thus not protected against fouling, which impairs its operational dependability.
The closest in the technical concept to the present invention is an automatic coupling device to connect the tractor and tractor-drawn means hydraulic systems, disclosed in the USSR Inventor's Certificate No. 580,993 (Int. Cl..sup.2 B60D 7/04, published Jan. 25, 1977), which comprises a panel with receiving unions, mounted on the tractor-drawn means, and a body with hollow plungers movable in corresponding bores in the body mounted on the tractor. Each plunger partly extends out of the bore in the body and defines by one of its end faces a bottom chamber below the plunger in the bore. The operatively engaging end faces of the hollow plungers and of the receiving unions are fitted with spring-loaded shut-off ball valves. The bottom chambers are intercommunicated, and the hollow of each of the plungers communicates via a union in the side wall of the plunger portion extending out of the bore with the pressure or the drain line of the tractor hydraulic system, the bottom chambers periodically communicating via spring-loaded check valves carried by the plungers with the hollow of one or another plunger.
The shut-off valves provided in this device on the operatively engaging end faces of the plungers and of the receiving unions protect the device and the hydraulic system from fouling, but the provision of the spring-loaded check valves inside the plungers complicates the construction of the device and its operation, since the effort of the check valve springs must be accurately calibrated to conform with the working pressure of the fluid in the hydraulic system. Moreover, an accidental pressure drop in the hydraulic system due to a fluid leak through a check valve may cause the engaged parts of the device to disconnect from each other, which is particularly undesirable when the tractor hydraulic system is connected to that of a hoisting means. The above drawbacks greatly impair the operational dependability of the device.
The present invention has as its aim to provide an automatic coupling device which, owing to a separate fluid feed into the bottom chamber and into the plunger hollow, ensures a reliable connection of the tractor and tractor-drawn means hydraulic systems.